assimilation rate; PMT, plug medium temperature; PPF, photosynthetic photon flux; QI, quality index. 1 Former Graduate Research Assistant; currently, Research Associate. 2 Professor. Research funded by a grant from the New York State Dept. of Agriculture and
Uniformity of growth response of impatiens (Impatiems wallerana Hook. f.) plug seedlings was examined in four identical growth rooms. Differences among growth rooms for dry weight, height, and leaf area of 10- to 24-day-old seedlings were generally not significant. During six experiments over 6 months, an individual growth room was maintained under contant baseline environmental conditions. Differences in growth response over time appear to be related to nutrition and irradiance levels. For three experiments with nearly identical irradiance, temperature, and nutrition levels, dry weight and height growth differences over time were only rarely significant. These results illustrate that rather unsophisticated growth rooms can provide consistent growth response over time among experimental units.
. Upon hypocotyl emergence, seedlings were irrigated with 16N–0.94P–12.3K water-soluble fertilizer (Jack’s LX Plug Formula for High Alkalinity Water; J.R. Peters, Allentown, PA) providing (mg·L −1 ): 100 N, 10 P, 78 K, 18 Ca, 9.4 Mg, 0.10 B, 0.05 Cu, 0
Little research has been conducted to determine the influence of fertilizer sources and rates on zoysiagrass (Zoysia japonica Steud.) establishment. Our objectives were to determine the influence of slow-release N sources, water-soluble N from urea, and N, P, and K combinations on rate of zoysiagrass establishment. Prior to field planting of zoysiagrass plugs, N rates of 98, 196, and 392 kg·ha-1 from ureaformaldehyde (UF, 38N-0P-0K), isobutylidine diurea (IBDU, 31N-0P-0K, and a composted sewage sludge (1.0N-0.9P-0.2K) were incorporated into a soil with existing high P (193 kg·ha-1) and intermediate K levels (86 kg·ha-1). In a separate study nitrogen from urea (46N-0P-0K, 195 kg·ha-1), P from treble superphosphate (0N-19P-0K, 126 kg·ha-1) and K from muriate of potash (0N-0P-32K, 103 kg·ha-1) also were incorporated before planting. Five months after planting, none of the slow-release N sources or N-P-K combinations had enhanced coverage of the zoysiagrass. No additional fertilizer was applied in the 2nd year. Although statistically significant differences were found among treatments by the end of the 2nd growing season, the actual increases in zoysiagrass coverage provided by the fertilizers were no greater than 5% more than the unfertilized zoysiagrass. In a 3rd study, N (49 kg·ha-1) from urea, applied as a topdressing either once, four, or seven times annually, resulted in a negative linear [coverage = 63.8 − 0.02 (kg N/ha per year), r 2 = 0.57] response in zoysiagrass coverage the initial year, but not in the 2nd year. Nitrogen from urea (49 kg·ha-1) applied bimonthly or monthly the 2nd year had a greater beneficial effect on zoysiagrass growth than topdressing or preplant incorporation of N the initial year.
Polyethylene glycol 8000 (PEG-8000) was applied to a soilless growing medium at the concentrations of 0, 15, 20, 30, 42, or 50 g·L-1 to impose controlled drought. Salvia (Salvia splendens F. Sellow. ex Roem & Shult.) seeds were planted in the growing medium to determine if controlled drought affects morphology and anatomy of salvia. Polyethylene glycol decreased emergence percentage and delayed emergence up to 5 days. Stem elongation of salvia treated with the five lowest concentrations was reduced up to 35% (21 days after seeding), and salvia were a maximum of 53% shorter and the canopy was 20% more narrow compared to nontreated seedlings 70 days after seeding. These morphological changes were attributed to PEG-8000 mediated reduction in leaf water potential (Ψw). The growing medium Ψw ranged from -0.29 to -0.85 MPa in PEG-8000 treated plants, and plant height was positively correlated with Ψw 21 days after seeding. Stem diameter of PEG-treated seedlings was reduced up to 0.4 mm mainly due to reductions in vascular cross-sectional area. Xylem cross-sectional area decreased more than stem and phloem cross-sectional area. Polyethylene glycol 8000 reduced vessel element number, but not diameter.
Plants grown in small containers often show limited growth due to low levels of aeration and water holding capacity in the medium. These levels can be changed by management practices such as medium compaction, medium wetness at time of container filling, container height and volume, peat : vermiculite ratio, particle size, and the use of a wetting agent. A modified equilibrium capacity variable model was applied to an investigation of media-container interactions for short containers (<5 cm tall). Predicted volume percentages for total porosity (TP), container capacity (CC), air space (AS), unavailable water (UW), and available water (AW) were developed from measured moisture retention data and container geometry. AS increased with: 1) increased particle size, 2) increased media moisture at time of container filling, 3) decreased medium compaction, 4) increased wetting agent concentration, 5) decreased ratio of peat : vermiculite, and 6) increased container height. Increased percent AW resulted from smaller particle size, increased media moisture at time of container filling, decreased container compaction, decreased wetting agent concentration, increased ratio of peat : vermiculite and decreased container height.
1 E-mail firstname.lastname@example.org . The author gratefully acknowledges student intern Michele Sumi for technical assistance, Davon Crest Farms for supplying strawberry plug plants, and BASF Corp. for providing prohexadione-Ca. Mention of a trademark
occurs after fertilization ( Greenberg, 1996 ). It may also result indirectly as a non-physiological cell death after the loss of their supply of nutrients and sugars as a result of inactivation of the phloem pathway ensuing from plugging of sieve plates
with the density of the cores packed in the laboratory portions of this research. Each filled container was planted with H. rosa-sinensis ‘Fort Myers’ plugs (Hatchett Creek Farms, Gainesville, FL). Each plant was placed in the center of the container
Broccoli (Brassica oleracea L. var. italica) head weights and yields are highly sensitive to plant densities (P) and rectangularity. Broccoli cultivars were grown at four plant spacings (2.2 to 8.6 plants/m2) and four N rates (O to 336 kg N/ha) in 1986 and 1987. In 1988, plug spacings, as above, were factorially combined with treatments of one, two, or three plants per plug. Head weight (w) data were fitted to the reciprocal model: 1/w = a + bp and the exponential model: w = AKP, where a, b, A, and K are constants. Nitrogen rate did not interact with p. In 1986 and 1987, both the reciprocal and exponential models fit the w data (expressed as w relative to wmax for each cultivar) with highly significant R 2 values of 0.525 to 0.605. Yield equations derived from these models were asymptotic. In 1988, clumping (multiple plants per plug) reduced head weights but interacted with plant density. Only the exponential model could account for the assumption that clumping effects diminish as plant densities increase; the reciprocal model predicted the opposite effect. The exponential model was expanded to the form: w = CAKP, where C is proportionate reduction of w due to clumping. Derived yield models were asymptotic for the reciprocal model and parabolic for the exponential model.